The characterization
of single-molecule structures could provide
significant insights into the operation mechanisms of functional devices.
Structural transformation via isomerization has been extensively employed
to implement device functionalities. Although single-molecule identification
has recently been achieved using near-field spectroscopy, discrimination
between isomeric forms remains challenging. Further, the structure–function
relationship at the single-molecule scale remains unclear. Herein,
we report the observation of the isomerization of spiropyran in a
single-molecule junction (SMJ) using simultaneous surface-enhanced
Raman scattering (SERS) and conductance measurements. SERS spectra
were used to discriminate between isomers based on characteristic
peaks. Moreover, conductance measurements, in conjunction with the
principal component analysis of the SERS spectra, clearly showed the
isomeric effect on the conductance of the SMJ.